Ball and socket joint

ABSTRACT

A ball-and-socket joint for a motor vehicle, especially for the chassis of the motor vehicle has a ball-and-socket joint housing (i), which has a joint opening and in which a bearing shell ( 5 ) made of an insulating material is arranged. A ball pivot ( 4 ) is made of an electrically conductive material and has a joint ball ( 2 ) and a pivot ( 3 ) mounted rotatably and pivotably with its joint ball ( 2 ) in the bearing shell ( 5 ) and protrudes with its pivot ( 3 ) from the ball-and-socket joint housing ( 1 ) through the joint opening. An electrode ( 14 ) is arranged in the wall ( 12 ) of the bearing shell ( 5 ) at a spaced location from the joint ball ( 2 ), and the electrode ( 14 ) and the joint ball ( 2 ) are electrically insulated against each other via the bearing shell ( 5 ).

FIELD OF THE INVENTION

The present invention pertains to a ball-and-socket joint for a motorvehicle, especially for the chassis of the motor vehicle, with aball-and-socket joint housing which has a joint opening and in which abearing shell manufactured from an insulating material is arranged, witha ball pivot, which is made of an electrically conductive material, hasa joint ball and a pivot, is mounted with its joint ball rotatably andpivotably in the bearing shell and protrudes with its pivot from theball-and-socket joint housing through the joint opening.

BACKGROUND OF THE INVENTION

Such a ball-and-socket joint is described in the German patentapplication DE 100 09 054.0, where the ball-and-socket joint housingmade of an electrically conductive material is connected via electriclines to an evaluating unit, by means of which excessive wear of thebearing shell, which is characterized by the direct contact of the jointball with the ball-and-socket joint housing, can be detected.

DE 199 18 869 A1 discloses a ball-and-socket joint for vehicle steeringknuckles, which has a joint housing and a joint pin, which is mountedrotatably and deflectably in a two-part bearing shell made preferablyfrom a polymeric material by means of a spherical bearing surface,wherein the bearing shell itself is arranged in the joint housing. Awear indicator insert, which protrudes from the sealing washer in thenonworn state of the ball-and-socket joint on the side of the sealingwasher facing away from the bearing shell, is inserted into a sealingwasher fixed in the housing under pretension against the bearing shell.This pretension decreases with increasing wear of the ball-and-socketjoint, so that the wear indicator insert can be moved by an operator andcan be pressed into the sealing washer from the side of the sealingwasher facing away from the bearing shell. When the wear indicatorinsert can be moved or pressed into the sealing washer to the extentthat it no longer protrudes from the sealing washer on the side of thesealing washer facing away from the bearing shell, this indicates thatthe ball-and-socket joint is worn.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a ball-and-socketjoint in which excessive wear of the bearing shell can be detected in asimple manner without an operator having to perform a manual checking atthe site of the ball-and-socket joint.

A ball-and-socket joint is provided according to the present inventionfor a motor vehicle, especially for the chassis of the motor vehicle,where the ball-and-socket joint has a ball-and-socket joint housingwhich has a joint opening and in which a bearing shell made of aninsulating material is arranged and has a ball pivot which is made of anelectrically conductive material and has a joint ball and a pivot. Theball pivot is mounted with its joint ball rotatably and pivotably in thebearing shell and protruding with its pivot from the ball-and-socketjoint housing through the joint opening. An electrode is arranged in thewall of the bearing shell at a spaced location from the joint ball, theelectrode and the joint ball being electrically insulated against eachother via the nonworn bearing shell.

Electrically insulating material of the bearing shell, whichelectrically insulates the joint ball against the electrode, is locatedbetween the electrode and the joint ball in the nonworn state of thebearing shell. The thickness of the material of the bearing shellpresent between the electrode and the joint ball, which thickness is setat the time of the manufacture, decreases with increasing wear until thejoint ball directly touches the electrode. This state of contact can bemeasured by means of an electric evaluating device, which is connectedto both the electrode and the ball pivot via electric lines.

Using an evaluating means, a signal can be sent to the vehicle driver byactivating an optical or acoustic signal transmitter in the interiorspace of the vehicle when the joint ball and the electrode touch eachother. However, it is possible when there is an electric contact betweenthe electrode and the joint ball to send a signal to a digital computerprovided in the motor vehicle or to another means storing readableinformation, so that an information characterizing the wear of theball-and-socket joint is stored in the memory, which can be polled,e.g., in the case of maintenance work or, e.g., also via a radio signalat a receiver located at another location (e.g., in a workshop or at themotor vehicle manufacturer).

How much material can be removed from the bearing shell until thecontact between the joint ball and the electrode is closed and thebearing shell must be considered worn can be determined from thethickness of the material of the bearing shell that is present betweenthe electrode and the joint ball at the time of the manufacture of thejoint ball.

The electric evaluating device, which can be or is connected to theball-and-socket joint according to the present invention via electriclines, may be arranged at a distance from the site of theball-and-socket joint, so that an excessive wear of the bearing shellcan be detected in a simple manner without an operator having to performa manual checking at the site of the ball-and-socket joint.

The electrode may be designed as a pin arranged in the bearing shell.This pin may be designed as a cylindrical pin or as a pin that can bescrewed in with a thread.

However, the electrode is preferably designed as a ring-shaped electrode(ring electrode), so that the wear can be monitored independently fromthe direction of the principal load of the ball-and-socket joint. Thus,the ball-and-socket joint does not have to be aligned with the electrodeto the direction of the principal load during the installation in thevehicle. It is correspondingly also possible in the sense of the presentinvention to provide a plurality of electrodes arranged in a distributedpattern within the bearing shell.

Furthermore, it is possible to design the electrode as a foil or printedcircuit board enclosed in the material of the bearing shell or as avapor-deposited or metallized layer.

If the ball-and-socket joint housing is made of an electricallyconductive material and the electrode is connected to theball-and-socket joint housing, an electric contact may also developbetween the ball pivot and the electrode in the nonworn state of thebearing shell when the ball pivot is deflected in relation to theball-and-socket joint housing to the extent that the transition area ofthe ball pivot, which is present between the joint ball and the pivot,abuts the edge of the ball-and-socket joint housing surrounding thejoint opening. The electric contact between the joint ball and theelectrode would be closed in this case only via the ball-and-socketjoint housing rather than directly, and special insulation measures aretherefore necessary to avoid this. It is therefore proposed that theball pivot be provided with a collar made of an electrically insulatingmaterial in the transition area provided between the joint ball and thepivot. An electric contact is thus reliably prevented from developingbetween the ball pivot and the edge of the ball-and-socket joint housingsurrounding the joint opening.

The components used in the chassis of a motor vehicle are usually madeof a metallic material and consequently an electrically conductivematerial. This may lead to the undesired effect that the electrode andthe ball pivot of the ball-and-socket joint mounted in the chassis areindirectly connected to one another electrically via the chassis partsif the ball-and-socket joint housing is made of an electricallyconductive material and the electrode is not insulated electricallyagainst the ball-and-socket joint housing. According to a variant of theball-and-socket joint according to the present invention, the pivot istherefore surrounded by an electrically insulating material in aring-shaped pattern on its end area facing away from the joint ball.Thus, an electrically insulating layer is present between the ball pivotand the chassis part to which the pivot is fastened, as a result ofwhich a direct electric connection is reliably prevented from developingbetween the ball pivot and the chassis part in question.

If the ball pivot surrounded by electrically insulating material in aring-shaped pattern is connected to a chassis part via an additionalfastening means, this fastening means shall preferably also be arrangedor designed in an electrically insulated manner in relation to the ballpivot and/or the chassis part. If, e.g., the pivot is provided with athread at its end facing away from the joint ball and the fasteningmeans is designed as a nut that is made of a metallic material and canbe screwed onto the thread, an insulating plain washer may be arrangedbetween the nut and the chassis part in order to prevent an electricallyconductive contact between the nut and the chassis part.

The electrode may be designed, furthermore, as a projection that is madein one piece with the ball-and-socket joint housing and is aligned withthe joint ball in the interior of the ball-and-socket joint housing.However, the electrode is preferably designed as a separate component,so that the bearing shell and the electrode can be assembled before themounting of the bearing shell into one assembly unit, which is theninserted into the ball-and-socket joint housing.

The electrode may be sealed in the plastic housing. However, theelectrode is preferably inserted into a recess that is provided in thewall of the bearing shell and is open toward the ball-and-socket jointhousing, the electrode being fixed in the recess, e.g., by means of asnap connection or with the use of an adhesive.

The recess may be designed in the form of a hole for receiving apin-shaped electrode or in the form of an internal thread for receivingan electrode designed as a threaded pin. However, the recess ispreferably an annular groove, so that the electrode can be inserted intothe annular groove at any point of the annular groove. However, theelectrode designed as a ring electrode is especially preferably insertedinto the annular groove.

The electrode may be in electric contact with the ball-and-socket jointhousing, the electrode being able to be contacted via a contact of theball-and-socket joint housing. However, the electrode is preferablyelectrically insulated against the ball-and-socket joint housing, sothat electrical insulation of the ball pivot against the ball-and-socketjoint housing and/or against a chassis part connected to theball-and-socket joint can be eliminated. Furthermore a lubricantintroduced into the interior space of the ball-and-socket joint cannotadversely affect the wear measurement any longer if the ball-and-socketjoint housing is made of an electrically conductive material, becauseleak currents between the electrode and the joint ball via theball-and-socket joint housing and the lubricant, which leak currentsdistort the wear measurement, are now reliably prevented from developingbefore the onset of the state of complete wear. The state of completewear is characterized here by the direct electric contact between theelectrode and the joint ball.

An electric line necessary for contacting the electrode may be led outof the ball-and-socket joint housing via the joint opening. To preventundesired foreign substances from penetrating through this jointopening, corresponding sealing measures should, of course, be takenagainst the environment.

It is also conceivable to arrange, e.g., a contact device designed as aplug-type connection on the ball-and-socket joint housing. However, aduct, through which an electric line, which is connected to theelectrode and is electrically insulated against the ball-and-socketjoint housing, extends out of the ball-and-socket joint housing, ispreferably provided in the housing. Thus, the electric line does nothave to be led through a sealing bellows, or be brought into contactwith one of the sealing surfaces of a sealing bellows, as a result ofwhich possible losses of tightness can be prevented in the area of thejoint opening.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partially cut-away view of an embodiment of theball-and-socket joint according to the present invention; and

FIG. 2 is a sectional view of the electrode in the form of a printedcircuit board enclosed within a bearing shell and connected to anincandescent lamp.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, The figure shows a partiallycut-away view of an embodiment of the ball-and-socket joint according tothe present invention. A ball pivot 4 having a joint ball 2 and a pivot3 is mounted rotatably and pivotably in a bearing shell 5 in aball-and-socket joint housing 1. A sealing bellows 6, which is sealinglyin contact with the ball-and-socket joint housing 1 by one of its endsand with the pivot 3 by its other end and prevents dirt and water frompenetrating into the interior of the ball-and-socket joint housing 1, isarranged between the ball-and-socket joint housing 1 and the ball pivot4. The two ends of the sealing bellows 6 are centripetally pretensionedvia a straining ring 7 and 8 each. A thread 9, on which a nut 10 isscrewed, is provided at the end area of the pivot 3 facing away from thejoint ball 2. Furthermore, the ball pivot 4 is surrounded by a collar 11made of an electrically insulating material in the transition areabetween the joint ball 2 and the pivot 3.

A recess 13, which is open toward the ball-and-socket joint housing 1and into which an electrode 14 is inserted and fixed by means of anadhesive, is provided in the wall 12 of the bearing shell 5. Via a firstelectric line 16 led through a duct 15 provided in the ball-and-socketjoint housing 1, the electrode 14 is electrically connected to anincandescent lamp 17 (or another optical signal transmitter), whoseother terminal is connected to the positive pole (+) of a power source.Both the first electric line 16 and the electrode 14 are designed heresuch that they are electrically insulated against the ball-and-socketjoint housing 1.

The ball pivot 4 is connected with its pivot 3 to the negative pole (−)of the power source via a second electric line 18, so that a closedelectric circuit is formed in case of an electrical connection betweenthe ball pivot 4 and the electrode 14, and the incandescent lamp 17 goeson.

The maximum allowable wear of the bearing shell 5 can be set byselecting the thickness Δ of the area of the bearing shell 5 locatedbetween the electrode 14 and the joint ball 2 at the time of themanufacture of the ball-and-socket joint, because the distance Δdecreases with increasing wear until an electric contact is finallyformed between the joint ball 2 and the electrode 14. The circuit isclosed at this moment, so that the incandescent lamp 17 goes on. If theincandescent lamp 17 is arranged in the interior space of the motorvehicle, the driver of the vehicle can determine from the lighting ofthe incandescent lamp 17 that the bearing shell 5 of the ball-and-socketjoint is worn.

FIG. 2 is a sectional view of the electrode in the form of a printedcircuit board 14′. The printed circuit board 14′ is located in thebearing shell 5′. The electric line 16 connects the printed circuitboard 14′ to the incandescent lamp 17.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

1. A ball-and-socket joint for a motor vehicle, the ball-and-socketjoint comprising: a ball-and-socket joint housing with a joint opening,said ball-and-socket joint housing being composed of an electricallyconductive material; a bearing shell made of an insulating materialarranged in said housing; a ball pivot made of an electricallyconductive material, the ball pivot having a joint ball and a pivotmounted rotatably and pivotably with said joint ball in said bearingshell and protruding with said pivot from said ball-and-socket jointhousing through said joint opening; an electrode arranged in a wall ofsaid bearing shell at a spaced location from said joint ball, saidelectrode and said joint ball being electrically insulated with respectto each other via said bearing shell disposed between said electrode andsaid joint ball, said electrode being electrically insulated withrespect to said ball-and-socket joint housing; and an electrode signalconnection line connected to said electrode and extending from saidelectrode through said ball-and-socket joint housing, said electrodesignal connection line being electrically insulated with respect to saidball-and-socket joint housing.
 2. A ball-and-socket joint in accordancewith claim 1, wherein said electrode has a ring-shaped design.
 3. Aball-and-socket joint in accordance with claim 1, wherein said ballpivot is surrounded by a collar made of an electrically insulatingmaterial in a transition area between said joint ball and said pivot. 4.A ball-and-socket joint in accordance with claim 1, wherein said pivotis surrounded by electrically insulating material in a ring-shapedpattern at least at its end area facing away from said joint ball.
 5. Aball-and-socket joint in accordance with claim 1, wherein said electrodeis designed as a separate component.
 6. A ball-and-socket joint inaccordance with claim 1, wherein a recess, which is open toward saidball-and-socket joint housing and into which said electrode is inserted,is provided in said wall of said bearing shell.
 7. A ball-and-socketjoint in accordance with claim 6, wherein said recess is designed as anannular groove.
 8. A ball-and-socket joint in accordance with claim 1,wherein said electrode signal connection line is an electricallyinsulated line, said ball-and-socket joint housing having a duct,through which said electrically insulated electric line, which isconnected to said electrode and is electrically insulated with respectto said ball-and-socket joint housing, extends from said ball-and-socketjoint housing, said electrically insulated line being provided in andextending through said ball-and-socket joint housing, said joint ballhaving a diameter that is greater than a transverse diameter of saidduct.
 9. A ball-and-socket joint for a motor vehicle, theball-and-socket joint comprising: an electrically conductiveball-and-socket joint housing with a joint opening; a bearing shell madeof an insulating material arranged in said housing; a ball pivot made ofan electrically conductive material, the ball pivot having a joint balland a pivot mounted rotatably and pivotably with said joint ball in saidbearing shell and protruding with said pivot from said ball-and-socketjoint housing through said joint opening; an electrode electricallyinsulated against said ball-and-socket joint housing and arranged in awall of said bearing shell at a spaced location from said joint ball,said electrode and said joint ball being electrically insulated againsteach other via said bearing shell; and a duct provided in saidball-and-socket joint housing, an electrically insulated electric linebeing connected to said electrode and being electrically insulatedagainst said ball-and-socket joint housing, said electrically insulatedline extending through said duct and from said ball-and-socket jointhousing.
 10. The ball-and-socket joint according to claim 9, whereinsaid electrically insulated electric line is directly electricallyconnected to said electrode.
 11. The ball-and-socket joint according toclaim 9, wherein said electrode has a rectangular cross section.
 12. Theball-and-socket joint according to claim 9, wherein said bearing shellhas a cylindrical section and at least one of an inclined and afrustum-shaped section, said electrode arranged in said inclined sectionof said bearing shell.
 13. The ball-and-socket joint according to claim9, wherein said electrode has a ring-shaped design.
 14. Theball-and-socket joint in accordance with claim 9, wherein said bearingshell has a tapered or frustum-shaped section.
 15. The ball-and-socketjoint in accordance with claim 14, wherein said a tapered orfrustum-shaped section adjoining a tapered or frustum-shaped section ofsaid ball-and-socket joint housing, said electrode being arranged in thetapered or frustum-shaped section of said bearing shell.
 16. Theball-and-socket joint in accordance with claim 15, wherein said jointball has a diameter greater than transverse diameter of said duct.
 17. Aball-and socket joint comprising: a ball-and-socket joint housing with ajoint opening, said ball-and-socket joint housing being composed of anelectrically conductive material; a bearing shell made of an insulatingmaterial arranged in said housing; a ball pivot made of an electricallyconductive material, the ball pivot having a joint ball and a pivotmounted rotatably and pivotably with said joint ball in said bearingshell and protruding with said pivot from said ball-and-socket jointhousing through said joint opening; an electrode arranged in a wall ofsaid bearing shell at a spaced location from said joint ball, saidelectrode and said joint ball being electrically insulated with respectto each other via said bearing shell disposed between said electrode andsaid joint ball, said electrode being electrically insulated withrespect to said ball-and-socket joint housing, said electrode beingdesigned as a printed circuit board; and an electrode signal connectionline connected to said electrode and extending from said electrodethrough said ball-and-socket joint housing, said electrode signalconnection line being electrically insulated with respect to saidball-and-socket joint housing.